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Allometria della lunghezza alare degli Odonati - differenze tra le famiglie e in relazione al comportamento migratorio
No full textWing length allometry in Odonata - differences between families in relation to migratory behaviour
No full textIn insects, wing shape and body size are correlated with several aspects of behaviour, and the optimal morphology of wings is a trade-off between a number of functional demands in relation to behaviour (e.g. foraging, migration and sexual display). Dragonflies are spectacularly skilful flyers, and present a range of different wing shapes, but to date no detailed studies have been conducted in this group on wing length allometry in relation to body size. In this paper we use published data on body length and wing length in all European and North American dragonflies to investigate differences in wing length allometries among Odonata taxa (suborders and families), and to relate these to behavioural patterns. We found different wing allometries between Zygoptera and Anisoptera, which are probably related to the flight mode and wing form of the two suborders. Among the Anisoptera, the Libellulidae showed a distinct wing length allometry from all other anisopteran families and migrants differed from non-migrant species. The first dichotomy is likely to reflect the adaptation of wing morphology of Libellulidae to sit-and-wait behaviour and to brief foraging flights (most species of this family are perchers) with respect to all other families, members of which are typically flyers . The second dichotomy reflects the trend of migrating species to have relatively longer wings than non-migrating members of the same family. Finally, wing length allometry differed among all the zygopteran families analysed, and this pattern suggested that each family evolved a particular wing morphology in response to peculiarities in behaviour, habitat and flight mode
Assessment of morphological and ecological conditions of Italian alpine rivers using IQM and Odonata
No full textUtilizzo degli Odonati come indicatori dello stato ecologico dei corsi d’acqua e strumento di monitoraggio di interventi di riqualificazione fluviale
No full textThe Odonate Habitat Index (OHI) revisited: an improved methodology tested in six Alpine Italian rivers
No full textSeasonal constraints influence Lucanus cervus mandible allometry (Coleoptera: Lucanidae)
No full textIn insects, allometries of exaggerated traits such as horns or mandibles are often considered species specific and constant
during a season. However, given that constraints imposed by the advancing season affect the developmental processes of organisms,
these allometries may not be fixed, and the switch point between morphs may vary between populations and within populations
during a season. The hypothesis of such a seasonal variation in exaggerated traits was tested using the dimorphic males of the beetle
Lucanus cervus. The remains of specimens killed by predators were collected along forest tracks from mid May to late August 2008
in a protected lowland forest in northern Italy. The largest beetles were collected in mid May and average size thereafter decreased.
Males collected early in the season mostly had large mandibles (i.e. they belonged to the major morph). In contrast, late in the
season the probability of finding males with large mandibles was very low. The threshold body size determining morph expression
also shifted during the season. Early in the season, the threshold pronotum width for a 50% chance of developing into the major
morph was 1.74 cm, whereas later in the season it was 1.90 cm. This shift in the threshold body size was interpreted as the effect of phenotypic plasticity in a population exposed to constraints imposed by the advancing season
Assessment of morphological and ecological conditions of Italian alpine rivers using the Morphological Quality Index (IQM) and Odonata
No full textWing allometry in Odonata – differences between fanilies and in relation to migratory behaviour
No full textSampling and comparing odonate assemblages by means of exuviae: statistical and methodological aspects
No full textFreshwater species are in serious decline all over the world. Thus, monitoring of freshwater ecosystems and species is crucial to guide policy actions and dragonflies are generally considered to be good indicators for these systems. The aquatic life stage of the Odonata is inherently more susceptible to changes in water quality than the imago and therefore exuviae give better insights into site-specific effects. However, utilizing exuviae for monitoring purposes introduces a number of problems. For example, they often do not persist long in the environment. Some of these problems have been addressed. However, there are no published data that distinguish the influence of sampling frequency and total sampling effort on the faunal completeness. Also the number of exuviae necessary to define local assemblages has not been investigated. These questions were addressed by analyzing the data on exuviae collected in seven sites and we found that for any given total amount of time invested, it was always preferable to conduct more short surveys, rather than fewer surveys lasting longer. The study also showed that a sample size of 300 exuviae allowed us to reliably estimate the similarity of two assemblages from different sites. However, when collecting 40 exuviae or less, the reliability was low. Based on our findings we recommend sampling exuviae for a minimum of 5 days, evenly spread out over the entire season during which Odonata emerge, to sample each time for approximately 60 min and aim to collect not less than 300 exuviae in total
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